THEY may look like lovable pets but Britain's estimated 9m domestic cats are being blamed by scientists for infecting up to half the population with a parasite that can alter people's personalities.

The startling figures emerge from studies into toxoplasma gondii, a parasite carried by almost all the country's feline population. They show that half of Britain's human population carry the parasite in their brains, and that infected people may undergo slow but crucial changes in their behaviour.

Infected men, suggests one new study, tend to become more aggressive, scruffy, antisocial and are less attractive. Women, on the other hand, appear to exhibit the “sex kitten” effect, becoming less trustworthy, more desirable, fun- loving and possibly more promiscuous.